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E. BLOCK OR SECTIOi1AL TANKS <br />(1) Rectangular Blocks <br />(a) Rectangular blocks shall be laid on an approved bottom. Block shall <br />be at least eight inches thick, constructed of a 4,000 psi core test <br />concrete mix, and cured to a 28 -day strenth before installation. <br />(b) Rectangular blocks shall <br />be laid <br />either with mortar <br />joints or filled <br />cores. <br />(c) There shall be <br />at le. <br />two coats <br />of 1/4 -inch thick <br />concrete plaster <br />placed on the <br />insid. <br />-ie block <br />tank. There shall <br />be at least two <br />hours elapsed <br />time <br />coats. <br />The plaster coat <br />shall start at the <br />bottom course <br />and .,. <br />.. <br />(2) Circular Block Tanks <br />(a) Circular blocks shall be carefully placed on an approved bottom. <br />Circular blocks shall be at least two inches thick and constructed of <br />a 4,000 psi core test concrete mix, cured t a 28 -day strength before <br />installation. <br />(b) There shall be at least two coats of 1/4-1. '. thick concrete plaster <br />placed on the inside of the block tank. There shall be at least two <br />hours elapsed time between coats. The plaster coag. shall start at <br />the bottom coarse and work up. <br />(3) Sectional Tanks <br />(a) A sectional tank shall have an entire section cast as an integral <br />unit. <br />(b) A sectional tank shall have two jr more sections and shall have at <br />least one joint below the level of the outlet invert of the tank. <br />(c) Sectional tanks shall have an integrally cast bottom, or shall.te <br />laid on an approved bottom. <br />(d) The joint or joints shall be permanently sealed so as to be <br />watertight. <br />(4) Bottoms <br />(a) Any tank not having an integrally cast bottom shall not oe installed <br />when the water table is closer than three inches to the bottom of the <br />excavation. <br />(b) If the bottom is poured -in-place concrete, It shall be a• least four <br />inches thick and extend to at least four inches outside the tank wsl'. <br />A concrete mix of at least one part cement, two parts washed sand, and <br />three parts washed rock shall be mixed before placement in the <br />excavation. <br />.2. <br />